In a cross-sectional epidemiological survey a selected group of former and present cement factory workers and a random sample of the corresponding urban population underwent dynamic spirometry. Based upon life experience the subjects were grouped into four occupational categories. Three hundred and one men were grouped as cement factory workers, 649 were grouped as blue collar workers, 218 as white collar workers and 102 men had predominantly been occupied in farming, forestry and fishing. On the average the investigated men had spent more than 75% of their total occupational life in their main occupational category. Each occupational category was further subdivided according to smoking habits and in all categories the well-known association between tobacco consumption and decrease in ventilatory capacity was found. White collar workers, who smoke less and had experienced better housing conditions throughout life had better ventilatory lung function than any of the other three occupational categories. No significant differences in lung function between cement factory workers and other blue collar workers with comparable smoking habits could be demonstrated by use of the maximal midexpiratory flow (MMEF), or any other of the calculated indices from the dynamic spirometry, when standardized for age, height and body weight.